The present invention relates to multimeters and particularly to multimeters for recording and displaying minimum and maximum readings as well as the time of occurrence of such readings.
Technicians repairing and debugging electrical equipment often wish to measure minimum and maximum values of voltage, resistance and the like at various points within a circuit or device under test. In addition it is helpful to know the time when a minimum or maximum value took place. Heretofore it has been necessary to observe the measurement instrument and manually record the minimum and maximum values as well as the times at which those values occurred. Such a method is undesirable in that the technician must remain at the location of the measuring instrument and monitor the operation thereof. Further, if the minimum or maximum event occurs for a short time span, it might pass unobserved. Thus the technician may miss the event while away from the work area or during a moment of inattention.
The minimum or maximum event may take place on an irregular basis or after an extended period of equipment operation, requiring long, tedious observation stints while awaiting the event, at which time the technician is hindered from undertaking other tasks and more efficiently using his time. The technician may also wish to determine minimum/maximum event times relative to a second event, e.g. initial device power-up. Heretofore, such a determination has required recording starting time and subsequently manually calculating relative elapsed time after noting the times for minimum/maximum events. It would be desirable to determine minimum and maximum values and the times when the minimum and maximum values were measured, without requiring constant observation and manual recording.
An alternate method of recording minimum/maximum event information involves using a data logging device. However, typical data logging devices have drawbacks. Currently available devices require setting event trigger values, and do not record and time stamp data unless the measured parameter exceeds a preset event trigger limit. This limitation requires an operator to have some knowledge of the approximate limit values before beginning measurement, often a difficult task when troubleshooting equipment problems of unknown origin. Improperly choosing a limit can result in no meaningful data being obtained if the limit is too high. If too low, then too much data is recorded. Further, data logging devices are relatively large and cumbersome and it would be desirable to provide a handheld device capable of recording maximum and minimum values as well as the times when those values occur red.